Aluminum-modified alginate fiber



United States Patent "ice U.s'.' ci. 99-14 4 Claims ABSTRACT OF THEDISCLOSURE Synthetic fibrous meat products are prepared by spinning aprotein/carbohydrate gel mixture into an aqueous coagulating solutioncontaining an alkali earth metal salt and a water-soluble aluminum salt.The resulting fibers are resistant to ion exchange and solubilizationwhen contacted with alkali metal salt.

This application is a continuation-in-part of Ser. No. 542,737 filedApr. 15, 1966, now abandoned.

The present invention relates to the preparation of a synthetic fibrousmeat product from aluminum-modified alkaline earth metal carbohydratefibers. In another aspect, the present invention relates to themodification of alkaline earth metal carbohydrate fibers by treatmentwith an aluminum salt to inhibit the deteriorating ion exchangeencountered by the fibers when they are heated in a solution of analkali metal salt.

The food industry has expended a great amount of effort in developingsatisfactory meat substitutes from protein. To'be satisfactory, thesubstitutes must be nutritious, must simulate the texture, flavor, andappearance of natural meat products and must retain their texture aftercooking, so that the mastication properties of the cooked productresembles cooked meat. The prior art has disclosedthe preparation ofsynthetic meat-like materials from various edible protein sources, bothvegetable and animal. The protein sources can be formed into fibers andfilaments which are coagulated in a suitable bath and oriented bystretching. The protein fibers can be rendered more insoluble to-waterby treating them with a salt in tows and mixed with a suitable ediblebinder so that a product resembling meat is produced.

Products, such as those discussed above, have limitations in that theycannot be baked, broiled, boiled, fried, etc., since they are heatlabile and, hence, do not retain their shape and texture when cooked.

Ishler et al. disclosed in U.S. Patent No. 3,093,483, which issued onJune 11, 1963, that food products which can withstand the hightemperatures encountered in cooking can be produced by: -(1) forming asolution of a polymeric carbohydrate gel precursor capable ofproducing-a continuous thermostable gel; (2) dispersing, throughout thesolution, a proteinaceous material (either inert or modifiable): (3)forming the combined sol into fibers, preferably by extruding through aspinnerette; (4) treating the fibers so formed to gel the precursor andtransform the proteinaceous material, if of a modifiable nature, fromits solution-state into a substantially solid state; and (5) binding thegelled fibers together by means of an edible-:binder to form meat-likeproducts. Although the process disclosed in this patent provides anexcellent thermostable product, the product has some limitations.Specifically, most people, before they consume the fibers, Want tofiavor them by use of table salt, i.e., sodium chloride. Usually, thesalt is added during cooking. The treatment of the fibers to gel theprecursor is a treatment with a solution of an alkaline earth metalcation, e.g., calcium. The' 3,455,697 Patented July 15, 1969 polymericcarbohydrate, before this treatment, is usually in the form of thealkali metal salt, e.g., sodium. The alkali metal carbohydrate is nottough and resilient; rather, it goes into solution in water. When theprecursor is gelled, an ion-exchange takes place with the alkaline earthmetal cation taking the place of the alkali metal cation and thusgelling the carbohydrate. However, when these fibers are boiled insodium (or other alkali metal) solution, ion-exchange again takes placewith sodium taking the place of the alkaline earth metal, thus renderingthe carbohydrate partially soluble in water.

It is, therefore, an object of the present invention to provide aprotein-carbohydrate fiber which can withstand treatment in boiling saltwater.

It is a further object of this invention to provide a process formodifying alkaline earth metal carbohydrate fibers so that thedeteriorating effects on the fibers of boiling in salt water areinhibited.

Accordingly, this invention provides a protein-carbohydrate fiber whichwill withstand the deteriorating effects of boiling in salt water. Theinvention comprises adding to the gelling bath, wherein the alkali metalcarbohydrate fibers are gelled by treatment with an alkaline earth metalat a slightly acidic pH, a small amount, e.g., 0.1 to 5.0% by weight ofa soluble aluminum salt such as aluminum chloride, aluminum acetate,aluminum chlorate, aluminum nitrate, and the like. Further, the additionof the aluminum salt enhances the resultant strength of the fiber.

Preferably, the process of the present invention comprises: (a) forminga dispersion of a proteinaceous material (e.g., an inert or a modifiableproteinaceous material) and a solution of a polymeric carbohydrate gelprecursor capable of producing a continuous thermostable gel; (b)forming the resulting dispersion into fibers, e.g., by extrusion througha spinnerette; and (c) treating the fibers so formed in a slightlyacidic, aqueous bath containing an alkaline earth metal cation andaluminum to gel the precursor and transform the proteinaceous material,if of a modifiable nature, from its solution state into a substantiallysolid state. The final fibers are usually arranged into tows and boundtogether by use of an edible binder to form a meat-like product.

The gelled fiber is comprised of aluminum and an alkaline earth metalcarbohydrate fiber. It has been found that the presence of aluminum in acarbohydrate fiber protected the system from deteriorating ion exchangewhich can occur if the fiber is heated in an alkali metal salt solution.That is, when, for example, calcium alginate fiber is heated in thepresence of sodium or potassium salts, the calcium alginate reverts tothe sodium or potassium alginate with the resultant loss in fiberstrength. The presence of aluminum in the fiber prevents the reversion.

The aluminum salt which is to be added to the gelling bath in thepresent invention can be any of the ionizable aluminum salts, such asaluminum cholride, aluminum sulfate, aluminuln nitrate, aluminumchlorate, and thelike,

including mixtures. The aluminum salt should be added in an amount offrom about 0.10 to 5.0% by weight of the bath depending upon the type offiber desired, i.e., large amounts of aluminum will give a hard andtough fiber while small amounts will give a fiber which is much moresusceptible to ion exchange.

The carbohydrate material used in this invention is selected from one ofthe many thermostable gel precursors such as those derived from alginsor pectins and like polymeric carbohydrates, e.g., alkali salts ofalginic acid earth metal ions such as calcium and the like. Thesealkaline earth metal cations serve to gel the precursor and also tocoagulate or to precipitate the protein, if the protein which is used isof a modifiable (i.e., precipitable or coagulable) nature. Ordinarily,the alkaline earth metal ion which is used is calcium acetate, and it ispresent in an aqueous solution.

Among the proteinaceous materials which can be employed are modifiableextracts of soybean meal, isolated proteins, peanut meal, fish proteinmeal, albumins, such as egg albumin and soy albumin, gelatin, caseinssuch as calcium paracaseinate and sodium caseinate, globulins,glutelins, and the like. Other color, flavor, and texture modifyingingredients can also be added. Among these are: oils, lard, chicken fat,tallow, beef extracts, chicken extracts, monosodium glutamate, dry skimmilk powder, and the like.

The temperature of the spinning dispersion can vary considerablyalthough it is usually held at about room temperature, 20-25" C. Theextrusion step of the process is usually conducted at slightly elevatedtemperatures and pressures, e.g., about 20-60 C. and to 100 p.s.i. ThepH of the spinning dispersion should be at least slightly acidic, e.g.,5.0 to 7.0, preferably 6.0 to 7.0.

As stated above, the gel precursor is gelled by treatment of the fibersimmediately after formation with an aqueous solution of a polyvalentcation, e.g., an alkaline earth metal ion such as calcium. A preferredbath is comprised of calcium acetate at slightly acidic conditions,e.g., at a pH of 4.5 to 6.0, preferably 5.0 to 5.5. The pH can beadjusted by the addition of a weak acid, preferably a Weak organic acid,such as acetic acid.

The protein, if of a modifiable form, is either precipitated by loweringthe pH of the bath to the isoelectric pH of the protein, or it iscoagulated by heating the fibers after the alkaline earth metal cationsolution treatment to gel the precursors. Alternatively, the protein canbe in a non-modifiable form, and the fibers therefrom would thus requireno treatment other than gellation of the polymeric carbohydrate gelprecursor.

Thus, it can be seen that this invention provides a novel fibrousmeat-like product which is not susceptible to alkaline earthmetal-alkali metal ion exchange when the product is heated in analkali-metal solution, and thus, the product will not break down incooking if the consumer desires to add table salt thereto.

The following examples further illustrate the objects and advantages ofthis invention, but the particular protein material, polymericcarbohydrate material, aluminum salt, alkaline earth metal salt, andtreating conditions should not be construed to unduly limit theinvention.

Example I An aqueous colloidal solution having the followingcomposition:

Fat (chicken) was extruded through a 204-hole spinnerette having holes0.015" in diameter into acoagulating bath containing 1.0% by Weightaluminum chloride, 1.0% by weight calcium oxide, 2.5% by weight glacialacetic acid, and 95.5% water.

The treated fibers which formed in the coagulating bath were washed withwater, after which a small amount of the fibers were boiled for 30minutes in an aqueous 1.0% solution of sodium chloride. The boiledmaterial was quite tough and was considerably tougher than a controlsample which was made by the same method as above except that thecoagulating bath contained 3.5% by weight calcium acetate and noaluminum chloride.

The rest of the washed fibers were arranged into tows and bound togetherby use of a small amount of an edible protein binder. These tows wereautoclaved and canned in a 0.5% sodium chloride solution. On standing,there was no noticeable discoloration nor was there a loss of toughness.The control sample suffered discoloration and loss of strength whencanned in a similar fashion.

Various modifications and alterations of this invention will becomeobvious to those skilled in the art from the foregoing descriptionwithout departing from the scope and spirit of the invention, and itshould be understood that this invention is not to be limited unduly tothat set forth herein for illustrative purposes.

I claim:

1. In a method for preparing an edible food product having a fibroustexture wherein a dispersion of protein and a polymeric carbohydrate gelprecursor is extruded into a fiber and the gel precursor is gelled bytreatment in an alkaline earth metal solution, the improvement whichcomprises adding to the alkaline earth metal solution a water-solublealuminum salt in an amount sutiicient to render the gelled fiberresistant to ion exchange when contacted with an alkali metal saltsolution.

2. The method of claim 1 wherein the aluminum salt is added in an amountof from 0.1 to 5% by weight.

3. The method of claim 1 wherein the aluminum salt is aluminum chloride.

4. An edible food product comprising an aggregation of treated polymericcarbohydrate fibers, each of said fibers being composed ofaluminum-alkaline earth metalpolymeric carbohydrate material which isresistant to alkali metal ion exchange, said product being prepared bythe method of claim 1.

References Cited UNITED STATES PATENTS 9/1886 Stanford 99l31 XR 6/1963Ishler et a1. 99-131 RAYMOND N. JONES, Primary Examiner J. R. HOFFMAN,Assistant Examiner US. Cl. X.R.

